1. Field of the Invention
The present invention relates to a battery provided with a rivet and a method of manufacturing such a battery, in which the rivet is inserted through a through hole in a battery case with a gasket interposed therebetween.
2. Description of the Related Art
JP-A-2003-157812 shows that this battery is provided with a battery case main body that contains a power generating element, and a lid that covers an opening of the battery case main body. A solid rivet (rivet terminal) is inserted through a through hole in the lid with a gasket interposed therebetween. A current collector is disposed on an internal side of the lid such that one end in an axial direction of the rivet projects from a through hole of the current collector, subsequently the rivet is swaged on the one end, and whereby the current collector is fixed and the gasket is closely attached to the lid to seal between the lid and the rivet.
The detailed configuration of JP-A-2003-157812 described above is illustrated in FIG. 7A. FIG. 7A shows the battery upside down for swaging, in which a rivet 21 is provided to have one end in an arc shape spreading sideways by swaging the one end of the rivet 21, and a current collector 22 is fixed to a lid 26 with two gaskets 24 and 25 interposed therebetween. Further, at this time, by transmitting a pressure applied to the rivet 21 to the two gaskets 24 and 25, the gaskets 24 and 25 are closely attached to the lid 26, and whereby the lid 26 and the rivet 21 are sealed.
However, as a distance from the one end of the rivet 21 to a central portion 21A in the axial direction (a length of an arrow in FIG. 7A) is long and the applied pressure may not easily be transmitted to the central portion 21A of the rivet 21 in the axial direction, it is not possible to sufficiently expand a diameter of the central portion 21A of the rivet 21 in the axial direction. This prevents the other gasket 25 (an annular projection of the other gasket 25 inserted into a through hole 26A in the lid 26) from closely attaching to an inner periphery of the through hole 26A, and therefore it is often not possible to reliably seal around the through hole 26A.
FIG. 7B shows method of using a hollow rivet 27 to seal between the hollow rivet 27 and the lid 26. The hollow rivet 27 is provided with a pair of tubular portions 27A and 27B each having one end and the other end open, and a flange 27C disposed between the tubular portions 27A and 27B. The hollow rivet 27 fixes the current collector 22 and a terminal block (bus bar) 23 to the lid 26 with two gaskets 28 and 29 interposed therebetween by being placed on a pedestal 20 and swaged on the both ends. In addition, the rivet 27 causes the gaskets 28 and 29 to be closely attached to the lid 26 to seal between the lid 26 and the hollow rivet 27 (see FIG. 7(c)).
However, in this case, although the applied pressure is transmitted by swaging the one end of the hollow rivet 27 and a diameter of a central portion 27D of the hollow rivet 27 in the axial direction can be expanded, there is a problem that not only the force to expand the diameter is small, but the diameter of the central portion 27D in the axial direction that is once expanded can become smaller due to an elastic restoring force of a lower tubular portion 27A as the lower tubular portion 27A is hollow. Therefore, practically, it is not possible to cause the gasket 29 (an annular projection of the gasket 28 inserted into the through hole 26A in the lid 26) to closely attach to the inner periphery of the through hole 26A, and therefore it is often not possible to reliably seal around the through hole 26A. Moreover, as a thickness of the tubular portion 27A of the hollow rivet 27 is even and thin, there is a problem that a base portion of the tubular portion 27A can be fused when a high current flows through the hollow rivet 27.